Weather Report: Tom Skilling 7-Day Forecast WGN-TV Weather Center.

Windy late week storm to mark fall's arrival

thundery 1+" rains, 70s likely

September 20, 2006|By Tom Skilling

More than an inch of rain may fall later this week and into the coming weekend as the latest in a parade of August/ September storms off the Pacific sweeps into the Midwest in an intensifying mode. Strengthening storms are very often windy storms. As air ascends in storms like the one predicted Thursday night into Saturday, winds increase as air pours into the system to replace the rising air. This embellishes the storm's moisture supply and increases the variation in temperature across it, which in turn, strengthens jet stream winds aloft. Since pockets of strong winds within the jet stream also act to lift and cool moist air, the situation feeds on itself, lowering air pressures while spinning up repetitive waves of thundery rainfall. Snows will whiten higher elevations of the Rockies, from Utah, Idaho, and Wyoming into Colorado over coming days. Strengthening southerly winds east of the storm reach Chicago by Friday boosting temperatures to the 70s.

Sources: NOAA-NCEP, Frank Wachowski, veteran Midway observer

WGN-TV/Thomas Valle, Brent Gilles and Zach Rodeghero

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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.